1. Field of the Invention
This invention relates to a bidirectional communication system, and more particularly to a communication system suitably used for executing a program such as TV-game software between multiple terminal units in common.
2. Description of the Prior Art
Establishments such as hotels or the like are equipped, for providing information services, a communication network extending in specific areas such as CCTV (Closed Circuit Television) system. CCTV system is a closed-circuit television system utilizing wired communication network, and is provided with a center unit for managing whole system within an establishment such as a hotel and a plurality of terminal devices connected to the center via cables. Utilizing a CCTV system, a hotel or the like presents special voluntary programs as well as general TV broadcasting programs. In a guest room of the hotel, people sometimes enjoy playing a TV game. However, in a CCTV system, a center unit is not allowed to transmit information necessary for the TV game due to some technological reasons. Therefore, guest rooms of a hotel are provided with a game equipment, respectively, and guests connect the game equipment with a TV monitor of a terminal unit of the CCTV system to play the TV game. FIG. 1 is a block diagram illustrating an example of an amusement system using game equipments and CCTV system in combination. As illustrated, terminal devices 200.sub.-1 to 200.sub.-n are installed in rooms R.sub.1 to R.sub.n, respectively. Converters 4 in the terminal devices 200.sub.-1 to 200.sub.-n are connected to a CCTV communication line 300 in the hotel and are supplied with video programs such as a TV broadcasting program or voluntary program transmitted from center 100. To each of the terminal devices 200.sub.-1 to 200.sub.-n are connected game equipments 3, and guests can connect the game equipment 3 to a TV monitor 5 via image input terminal of the converter 4 and enjoy the TV game with watching game images displayed on the monitor 5.
On the other hand, techniques utilizing a public communication line CATV (Cable-TV) system for enabling users of a terminal device to select and play one of a plurality of game programs stored in a center unit are disclosed in Japanese Patent Applications Laid-Open Nos. 63-99893 and 63-16739. Particularly, the system disclosed in the latter (Japanese Patent Applications Laid-Open No. 63-16739) enables a user to select a game program stored in a terminal device and the selected game program is read out and stored in the terminal device so that the user can enjoy the game. Namely, a registered user of the CATV line selects his/her favorite game program from a menu display on a TV monitor and requests the center to transmit the game program thus selected to his/her terminal device. In response, the center transmits the game program to the user's terminal device and the program is stored in a memory in the terminal device. As a result, the user can enjoy the game program as he/she plays it with general game equipment and game cartridge.
The above-mentioned technique utilizing a CCTV system does not have any alternative ways, other than providing game equipments in each guest rooms, respectively, to enable a user to play game programs from respective rooms. The center can send nothing more than a demonstration or attraction pictures relating to the game so that they are displayed on a monitor of the terminal device, and it is impossible to create a game playing circumstance in which the user can join in a game via a communication line. On the other band, the above-mentioned program supplying manner using a CATV system is advantageous in that it requires low cost compared with the above method of providing game equipments in each rooms, respectively, and that abundant game programs stored in the center unit can be efficiently used. However, such a system has the following shortcomings. Firstly, in such a system, a terminal unit merely reads one of a plurality of game softwares stored in a center unit, and it is impossible that multiple terminal units have access to a unique game at the same time. Secondly, plural people in a guest room cannot play the same game together until the game program is completely read out from the center unit and stored in the terminal unit. Namely, in the above-mentioned system, it is impossible to enable plural people in the same room to play the same game together without reading and storing the game program in the terminal unit, although the center can provide game amusement as one of abundant information services including movie, TV broadcasting, etc. Thirdly, it is also impossible that plural people in different guest rooms play the same game together, e.g., compete against each other for their scores.